Wet process for developing styrene polymer resists for submicron lithography

ABSTRACT

The invention is directed to a process for preparation of a negative resist configuration on a siliceous substrate. 
     A negative resist polymer is bonded to the siliceous substrate using an intermediary interlayer of silane between the substrate and the resist polymer. The silane is applied to the siliceous substrate and the silane-coated surface is heated to accomplish bonding; the resist polymer is then applied as an overlay on the silane-coated surface and the resist polymer surface is irradiated to form an image therein and simultaneously to bond the resist polymer image to the silane-coated surface. 
     The resist image is then developed using a developer solvent to remove resist polymer which was not irradiated, and the developer solvent is followed by a rinse solvent which, in one aspect, substantially eliminates any snaky lines or edges on the developed resist image, or in another aspect, by utilizing multiple rinses to accomplish the same and to also remove substantially all of the residual developer solvent trapped within the developed resist image, thus reducing swelling and returning the initial resist to about the same dimensions as the image prior to development.

The Government of the United States of America has rights in thisinvention pursuant to Contract No. N00123-79-C-0809 awarded by theDepartment of the Navy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to wet development of negative resist patterns(images). More particularly, the invention relates to the preparation ofnegative resist images substantially free of snaky lines or edges.Especially the invention relates to the preparation of negative resistimages substantially free of snaky lines or edges and of a thicknesssubstantially that of the initial resist layer. Further, the inventionrelates to the bonding of the irradiated resist to a siliceoussubstrate.

2. Description of the Prior Art

The invention is directed, in the main, to wet development of irradiatednegative resist to produce a pattern (image) which is substantiallyundistorted from the initial pattern prior to development. Specifically,the lines, edges, and profiles are substantially free from dimensionalchanges such as snaking or other distortions. This development processis used in conjunction with numerous negative resist polymers whichafford a range of radiation sensitivity.

When electron beam images with narrow lines, especially lines less thanone μm in width, are developed in negative resists, there is apronounced tendency for the lines and edges to undergo a characteristicsinusoidal deformation that can be named "snaking". Other observers havedescribed this line phenomenon as "sinuous lines", or "scriggily lines",or "wavy lines". These snaky lines form lateral filaments, in someinstances, which cause bridging of the adjacent lines; in severe cases,snaky lines may not only bridge but merge.

It has been observed that the developed negative resist is swollen andis thicker (higher) than the thickness (elevation) of the initial resistlayer. This increased thickness may introduce undesirable anomalies intothe developed resist; a developed resist having substantially thethickness of the initial resist layer is preferred.

The article, "Three Dimensional Behavior of Negative Electron Resists"by R. D. Heidenreich and G. W. Kammlott, Polymer Engineering andScience, June 1977, Vol. 17, No. 6, pp. 377-380, is concerned with theinfluence of swelling in the exposed (irradiated) resist during solventdeveloping. The polymer used was poly(glycidyl methacrylate-co-ethylacrylate). The developer was a solution mixture of methyl ethyl ketoneand ethanol; two proportions were used: 5MEK:2 ethanol and 5MEK:1.5ethanol. The development was by immersion. When the 5:2 solution wasimmediately followed by the 5:1.5 solution, the exposed resist developedlines were very scriggily. It was concluded that the poor edgedefinition of the developed resist is the result of swelling of thepartially cross-linked polymer in the liquid developer.

The article, "Sol-Gel Behavior and Image Formation in Poly(glycidylmethacrylate) and Its Copolymers with Ethyl Acrylate, by E. D. Feit, M.E. Wurtz and G. W. Kammlott, Journal of Vacuum Science and Technology,15(3), May/June 1978, pp. 944-947, is concerned with the interaction ofthe resist and the liquid developer. Seven samples of PGMA and eightsamples of P(GMA-co-EA) were tested, using a scanning electron beam. Thedeveloper was a solution mixture of ketone and alcohol (species notspecified) in proportions ranging from 3:1 to 9:1. In some instances, ahigh ratio solution immersion was followed by a lower ratio solutionimmersion. Owing to the swelling of the resist during development, linesdeform and assume a sinusoidal appearance. It was concluded thatfaithful reproduction in the resist of a feature written by the electronbeam does not depend on molecular parameters of the polymer alone, butrather on factors such as solvent induced swelling, competitive wettingof the substrate and of the polymer by the solvent, and gel rupture byforced development.

The article, "PGMA as a High Resolution, High Sensitivity NegativeElectron Beam Resist", by Yoshio Taniguchi et al, Japanese Journal ofApplied Physics, Vol. 18, No. 6, June 1979, pp. 1143-1148, is concernedwith comparing resist material and concludes that PGMA is, underappropriate conditions, an excellent resist material. The samples wereelectron beam exposed; the development was by immersion or spraying witha solution mixture of methyl ethyl ketone and ethanol. The developedsamples were rinsed for sixty seconds in methyl isobutyl ketone. Theoptimum developer was 6:1-10:1 solution mixture, with an immersion timeof 180 seconds (40 seconds by spraying). It was observed that someresists showed line deformaton, referred to as "rough edges", which wasattributed to post-baking temperatures.

The article, "Chloromethylated Polystyrene as a Dry-Etch-ResistantNegative Resist for Submicron Technology", by Saburo Imamura, Journal ofElectro-chemical Society: Solid-State Science and Technology, Vol. 126,No. 9, September 1979, pp. 1628-1630, is concerned with a new resistmaterial, chloromethylated polystyrene (CMS). As a resist material, CMSwas irradiated with X-rays and with deep UV-radiation. The exposed CMSresist was developed by dipping into n-amyl acetate solvent for thirtyseconds, and then rinsed in isopropyl alcohol for sixty seconds. Nomention is made of resist line or edge deformation.

The article, "Molecular Parameters and Lithographic Performance ofPoly(Chloromethylstyrene)--A High Performance Negative Electron Resist",by H. S. Choong and F. J. Kahn, Journal of Vacuum Science andTechnology, 19(4), November/December 1981, pp. 1121-1126, is concernedwith locating a resist material that is the equivalent of thechloromethylated polystyrene of Imamura (above). It is considered thatthe alkylation agent of Imamura is carcinogenic. It was found that thepoly(chloromethylstyrene) polymer was equal to the Imamura polymer. Thetests were carried out by exposing the resist with a scanning electronbeam. The exposed resist was developed by dipping into n-pentyl acetateand then rinsed in isopropyl alcohol (as was done by Imamura). It wasobserved that developed lines were wavy and showed some bridging,attributed to resist swelling and the proximity of the lines.

The article, "Sensitivity and Contrast of Some Proton-Beam Resists", byRobert G. Brault and Leroy J. Miller, Polymer Science and Engineering,Vol. 20, No. 16, Mid-November 1980, pp. 1064-1068, is the product of thepresent Applicants. Positive and negative resist polymers were testedfor proton-beam sensitivity. The styrene or substituted styrene polymerstested were: polystyrene, poly(4-chlorostyrene), poly(vinyltoluene),poly(vinylbenzyl chloride), poly(4-bromostyrene), poly(isopropylstyrene)and poly(4-tert-butylstyrene). A considerable range of sensitivity withboth proton beam and electron beam radiation was observed. Developmentwas by solvent only, using chlorobenzene or toluene.

The article, "A Method of Rapidly Screening Polymers as Electron BeamResists", by Robert G. Brault and Leroy J. Miller, Journal ofElectrochemical Society, Vol. 128, No. 5, May 1981, pp. 1158-1161, isthe product of the present Applicants. In discussing thepolymethacrylate positive electron resists, there is mentioned thepossible use of "additional rinses with weak solvents" but no detailsare set forth.

SUMMARY OF THE INVENTION

In one aspect of the present invention, the invention is directed to alithographic process for preparing a patterned resist on a substrate byapplying a layer of negative resist onto a substrate, which polymer isselected from the group consisting of polystyrene, halogenatedpolystyrene, and substituted styrene polymer having at least onesubstituent, where the substitutent(s) is independently selected fromthe group consisting of alkyl having 1-4 carbon atoms, halo, haloalkylhaving 1-4 carbon atoms and at least one halo; and mixtures thereof;irradiating the resist polymer to form a negative pattern image therein;and developing that image by (i) dissolving away unexposed polymer witha developer solvent (d/s), and (ii) rinsing the wet developed resistwith a rinse nonsolvent (r/ns) to eliminate substantially any snakinessof the developed resist pattern image; where the developer solvent/rinsenonsolvent combination is selected from the following Schedule 1:

    ______________________________________                                        Schedule 1                                                                    ______________________________________                                        I.   (d/s)    R.sub.2 --(OCH.sub.2 CH.sub.2).sub.m --O--H                          (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              II.  (d/s)    R.sub.7 --(OCH.sub.2 CH.sub.2).sub.m --O--R.sub.7                    (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              III. (d/s)    R--CO--(OCH.sub.2 CH.sub.2).sub.p --O--(OC).sub.0-1 --R              (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              IV.  (d/s)    benzene, toluene, ethylbenzene, xylene,                                       monochlorobenzene, monochlorotoluene,                                         monochloroethylbenzene, monochloroxylene,                                     ortho-dichlorobenzene, meta-dichloro-                                         benzene, and trichlorobenzene                                        (r/ns)   alkane having 5-8 carbon atoms, cyclo-                                        alkane having 5-8 carbon atoms, and                                           petroleum distillate boiling in the 5-8                                       alkane carbon atom boiling range                                V.   (d/s)    dioxane                                                              (r/ns)   R--OH                                                           ______________________________________                                    

where:

R is alkyl having 1-4 carbon atoms,

R₂ is alkyl having 4-8 carbon atoms,

R₅ is H, methyl, or ethyl,

R₇ is alkyl having 1-8 carbon atoms,

m is an integer equal to 1-4, and

p is an integer equal to 1-2.

In a second aspect of the present invention, the negative image isdeveloped by dissolving away the unexposed polymer with a developersolvent, and then the wet, developed resist is multiply rinsed in aseries of consecutive steps using successively weaker solvents andterminating with a nonsolvent. The negative image must be maintained ina wet condition during the series of rinsing steps described above. Useof this process substantially eliminates any snaky lines or edges on thedeveloped resist image and reduces or eliminates any swelling of theresist profile, so that the developed resist image is substantially thesame as the initial exposed image prior to development. The developersolvent/rinse nonsolvents combinations are selected from the followingSchedule 2, where the multiple series of rinses begins with (a) or amixture of (a) and (b) which is rich in (a) and progress toward only(b), and where the series of rinses encompasses a minimum of two rinses:

    ______________________________________                                        Schedule 2                                                                    ______________________________________                                        A.    (d/s)    R.sub.2 --OCH.sub.2 CH.sub.2).sub.m --O--H                           (r/ns)   (a) R.sub.5 --(OCH.sub.2 --CH.sub.2).sub.m --OH                               (b) R--OH                                                      B.    (d/s)    R.sub.7 --(OCH.sub.2 CH.sub.2).sub.m --O--R.sub.7                    (r/ns)   (a) R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH                                 (b) R--OH                                                      C.    (d/s)    R--CO--(OCH.sub.2 CH.sub.2).sub.p --O--(OC).sub.0-1 --R              (r/ns)   (a) R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH                                 (b) R--OH                                                      D.    (d/s)    R.sub.2 --(OCH.sub.2 CH.sub.2).sub.m --OH, mixed with                         R.sub.2 OH                                                           (r/ns)   (a) R.sub.2 --OH                                                              (b) R--OH                                                      ______________________________________                                    

where:

R is alkyl having 1-4 carbon atoms,

R₂ is alkyl having 4-8 carbon atoms,

R₅ is H, methyl or ethyl,

R₇ is alkyl having 1-8 carbon atoms,

m is an integer equal to 1-4, and

p is an integer equal to 1-2.

In a third aspect of the present invention, the invention is directedtoward a process for bonding of the negative resist polymer to thesiliceous substrate through use of an intermediary, interlayer ofsilane. In the process, a substantially unitary article is formed.

A layer of silane is applied to the surface of a siliceous substrate,which silane is:

    R.sup.i --(O).sub.0-1 --(R.sup.ii).sub.0-1 --Si--(R.sup.iii).sub.3

where:

R^(i) is acryloyl, methacryloyl, or vinyl, and when R^(i) is vinyl, thenthe moiety "(O)₀₋₁ " is absent;

R^(ii) is alkylene having 2-6 carbon atoms, or R^(iv) --NH--R^(v) whereR^(iv) is hydroxyalkylene having 2-6 carbon atoms and R^(v) is alkylenehaving 2-6 carbon atoms, and when R^(i) is vinyl, R^(ii) is absent;

R^(iii) is halo, or alkoxy having 1-6 carbon atoms, or alkoxyalkoxy haveat least 3-6 carbon atoms, or alkanoyloxy having a total of 2-5 carbonatoms, or alkyl having 1-6 carbon atoms, where the number of said alkylgroups present is not more than 2, and mixtures of the preceding.

The layer applied to the surface of the siliceous substrate may also bethe hydrolysis product of any of the above described silanes, whereinone or more of the R^(iii) groups are replaced by OH.

After application of the layer of silane, the silane-coated surface isheated to a temperature sufficient to permit a direct chemical bondingat the surface of the siliceous substrate. Typically the silane layer isheated to about 200° C. for a period of about five minutes.

A negative resist polymer resin is applied over the silane-coatedsurface; such resist polymer resin affords free radicals when subjectedto radiation. The resist polymer resin is then irradiated (in thedesired pattern) to simultaneously provide the exposed resist and form abond between the exposed resist polymer and the silane coating, suchthat a substantially unitary article is obtained.

DETAILED DESCRIPTION OF THE INVENTION Substrate

The submicron lithographic process of the invention utilizes a negativeresist polymer positioned on a suitable substrate. Illustrativesubstrates are glassy materials, such as silicon oxide, glass,polyimides, ceramics, metals, and semiconductors such as silicon andIII-V materials (such as GaAs), etc.

Note, however, that to have the bonding process described in the thirdaspect of the present invention, the substrate must have silica orsilicon at its surface.

Negative Resist Polymer

The negative resist polymer of the wet submicron lithographic process ofthe invention is selected from the group consisting of (a) polystyrene;(b) halogenated polystyrene; and (c) substituted styrene polymer havingat least one substitutent, where the substituent(s) is selected from thegroup consisting of alkyl having 1-4 carbon atoms, halo and haloalkylhaving 1-4 carbon atoms and at least one halo; and mixtures thereof.

Polystyrene is a solid material made by polymerizing vinylbenzene(styrene) monomer, as is well-known.

Halogenated polystyrene is a polystyrene which has been reacted tointroduce chlorine or other halogen into the aromatic rings, in a randommanner.

Substituted styrene polymer is prepared by polymerizing a substitutedstyrene monomer to form a solid polymer. The monomer may include one ormore substituents independently selected from the group consisting ofalkyl having 1-4 carbon atoms, halo and haloalkyl having 1-4 carbonatoms and at least one halo atom.

Illustrative halostyrene monomers include: 4-fluorostyrene,2,5-difluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene,2,4-dichlorostyrene, 2,5-dichlorostyrene, 2,6-dichlorostyrene,3,4-dichlorostyrene, 2-bromostyrene, 3-bromostyrene, and 4-bromostyrene.

Illustrative alkyl substituted styrene monomers include:4-methylstyrene, 4-ethylstyrene, 4-isopropylstyrene,4-tert-butylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene,2,6-dimethylstyrene, and 2,4,6-trimethylstyrene.

Substituted styrene monomers having both halo and alkyl substituents arereadily prepared from halotoluene, haloxylene and other substituted haloand alkylbenzenes.

Illustrative haloalkylstyrene monomers include: chloromethylstyrene(vinylbenzyl chloride), dichloromethylstyrene, trichloromethylstyrene,bis(chloromethyl)styrene, chloromethyl methylstyrene(chloromethylvinyltoluene), chloromethyl dimethylstyrene(chloromethylvinylxylene), chloromethyl chlorostyrene andchloromethyldichlorostyrene.

Illustrative defined styrene polymers are set out roughly in decreasingorder of preference for use in the process of the invention:

poly(4-chlorostyrene)

poly(4-bromostyrene)

poly(3-chlorostyrene)

poly(3,4-dichlorostyrene)

poly(chloromethylstyrene)

poly(2,6-dichlorostyrene)

poly(2,5-dichlorostyrene)

poly(4-tert-butylstyrene)

poly(4-isopropylstyrene)

poly(vinyltoluene)

halogenated polystyrene and

polystyrene.

It is to be understood that copolymers and terpolymers made from theabove-defined monomers are suitable negative resist polymers.

The defined negative resist polymer is applied to the surface of thesubstrate directly, or through an appropriate bonding agent layer, inany conventional manner suitable to the particular polymer, to obtain aresist polymer coated wafer.

Irradiation

The resist polymer layer is irradiated to the desired pattern to obtaina latent image therein, by any suitable means, such as electron beam,proton beam, X-ray, UV-radiation, etc., as is well-understood in thisart.

Process I Development and Rinsing: General

Irradiation, or exposure, of the negative resist polymer produces alatent image of the desired pattern. This image is developed bytreatment with a developer which is a solvent for the unexposed polymer,followed by a rinse using what would be a nonsolvent for the unexposedpolymer, but which acts as a solvent for the developer solvent. Therinse permits removal of residual surface developer solvent andextraction of at least some of the developer solvent from within theresist image.

In order to distinguish these two solvents, they are referred to hereinas "developer solvent" (d/s) and "rinse nonsolvent" (r/ns). Also herein,a mixture of two solvents, solvent/nonsolvent, or two nonsolvents isreferred as a "solution mixture", which is a true solution of thecomponents.

It has been observed that the combination treatment of the inventionsubstantially eliminates any snaky lines or edges on the developedresist. It is thought the rinse nonsolvent shrinks thedeveloper-solvent-swollen resist enough to decrease the stress in theresist to the point where the snaky edge or line returns tosubstantially a straight resist profile.

The negative resist polymer is cross-linked during the exposure of thepattern (image) area to radiation, and becomes insoluble orsubstantially less soluble in the developer solvents than the polymer inthe non-exposed area(s). The solvent which dissolves away the nonexposedpolymer area is referred to as the developer solvent. The developersolvent is brought into contact with the polymer coated resist area bydipping (immersion), or by spraying the resist-wafer. The time ofcontact is dependent on the solvent and the method of contacting; ingeneral, for a given solvent, spraying gives the shortest time. Sprayingprovides continuously fresh solvent against the resist layer. However,the dipping or immersion may utilize two or more separate dips orimmersions into fresh solvent for each subsequent dip or immersion. Inwell-known manner, trial and error quickly determines the optimum timefor the particular developer solvent.

It is to be understood that the development procedure may use adifferent developer solvent for subsequent dips or immersions, andspraying may also be sequential. Also, the subsequent developer solventmay be a solution mixture of the developer solvent and of the rinsenonsolvent; this is in order to moderate the strength of the developersolvent.

The irradiated portion of the resist is essentially insoluble in thedeveloper solvent, but it is able to soak up some of the developersolvent; this soak-up results in a swollen developed resist. The rinsenonsolvent does not dissolve the irradiated resist. The rinse nonsolventwill remove residual developer solvent from the surface of the developedresist and from the wafer. The rinse nonsolvent will simultaneouslyextract some or all of the soaked-up developer solvent, from the swollencrosslinked resist image, which decreases the stresses which are thoughtto cause the undesirable snaky lines and edges.

The rinse nonsolvent may be brought into contact with the developedresist by any of the procedures used for the development (for example,dip, immerse and spray). If a dip development has been used, thedevelopment should be followed immediately by a dip into a fresh portionof the same developer solvent to eliminate resist polymer-developersolvent solution from adhering to the wafer, and also to preventre-precipitation of dissolved polymer onto the wafer surface, which canoccur when the wet developed resist is contacted by the rinsenonsolvent.

Development time is not particularly critical. It has been observed thatthe time can vary from 30 seconds or so to as much as 180 seconds withno adverse effects. The time in the rinse nonsolvent step also does notappear to be particularly critical; times have been varied over therange of about 15 seconds to 600 seconds (10 minutes).

It has been observed that better results are obtained when the developersolvent-wet-wafer is more or less immediately contacted with rinsenonsolvent. The developed resist should not become dry between thedevelopment treatment and the rinse nonsolvent treatment. Also, the wetresist condition should be maintained between sequential solventtreatment and sequential nonsolvent treatments.

It has been observed that certain resist polymers, after exposure,afford better quality developed images when there has been anintermediate development step. After the full strength developer solventtreatment of the exposed resist, a solution mixture of that developersolvent and of intended rinse nonsolvent is applied to the wet partiallydeveloped resist to complete the development. The normal rinsenonsolvent treatment follows.

Developer Solvent/Rinse Nonsolvent Combinations

In accordance with the invention, the developer solvent (d/s) rinsenonsolvent (r/ns) combinations useful in developing exposed resistimages and in straightening snaky lines and edges are presented informula form in Schedule 1, below.

    ______________________________________                                        Schedule 1                                                                    ______________________________________                                        I.   (d/s)    R.sub.2 --(OCH.sub.2 CH.sub.2).sub.m --O--H                          (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              II.  (d/s)    R.sub.7 --(OCH.sub.2 CH.sub.2).sub.m --O--R.sub.7                    (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              III. (d/s)    R--CO--(OCH.sub.2 CH.sub.2).sub.p --O--(OC).sub.0-1 --R              (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              IV.  (d/s)    benzene, toluene, ethylbenzene, xylene,                                       monochlorobenzene, monochlorotoluene,                                         monochloroethylbenzene, monochloroxylene,                                     ortho-dichlorobenzene, meta-dichloro-                                         benzene, and trichlorobenzene                                        (r/ns)   alkane having 5-8 carbon atoms, cyclo-                                        alkane having 5-8 carbon atoms, and                                           petroleum distillate boiling in the 5-8                                       alkane carbon atom boiling range                                V.   (d/s)    dioxane                                                              (r/ns)   R--OH                                                           ______________________________________                                    

where:

R is alkyl having 1-4 carbon atoms,

R₂ is alkyl having 4-8 carbon atoms,

R₅ is H, methyl, or ethyl,

R₇ is alkyl having 1-8 carbon atoms,

m is an integer equal to 1-4, and

p is an integer equal to 1-2.

The specific developer solvent/rinse nonsolvent combinations useful indeveloping exposed resist images and in straightening snaky lines andedges are presented in modified name form in Schedule 3, hereinafter.

    ______________________________________                                        Schedule 3                                                                    ______________________________________                                        E.   (d/s)    ethylene glycol mono-R--ether acetate, or                                     diethylene glycol mono-R--ether acetate,                                      or mixtures thereof                                                  (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 F.   (d/s)    ethylene glycol mono-R.sub.2 --ether, or                                      diethylene glycol mono-R.sub.2 --ether, or                                    mixtures thereof                                                     (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 G.   (d/s)    ethylene glycol di-R--ether, or                                               diethylene glycol di-R--ether, or                                             triethylene glycol di-R--ether, or                                            tetraethylene glycol di-R--ether, or                                          mixtures thereof                                                     (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 H.   (d/s)    ethylene glycol diacetate, or                                                 diethylene glycol diacetate, or                                               triethylene glycol diacetate, or                                              mixtures thereof                                                     (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 I.   (d/s)    dioxane                                                              (r/ns)   alkanol having 1-4 carbon atoms                                 J.   (d/s)    benzene, toluene, ethylbenzene, xylene,                                       monochlorobenzene, monochlorotoluene,                                         monochloroethylbenzene, monochloro-                                           xylene, ortho-dichlorobenzene, meta-                                          dichlorobenzene, and trichlorobenzene                                (r/ns)   alkane having 5-8 carbon atoms, cycloalkane                                   having 5-8 carbon atoms, and petroleum                                        distillate boiling in the 5-8 alkane                                          carbon atom boiling range                                       ______________________________________                                    

where:

R is alkyl having 1-4 carbon atoms

R₁ is alkyl having 1-2 carbon atoms

R₂ is alkyl having 4-8 carbon atoms

Illustrative developer solvents of "E" include:

ethylene glycol monoethyl ether acetate (2-ethoxyethyl acetate;Cellosolve acetate);

ethylene glycol monobutyl ether acetate (2-butoxyethyl acetate; butylCellosolve acetate);

ethylene glycol monomethyl ether acetate (2-methoxyethyl acetate; methylCellosolve acetate);

diethylene glycol monomethyl ether acetate;

diethylene glycol monoethyl ether acetate; and

diethylene glycol monobutyl ether acetate.

Illustrative rinse nonsolvents of ethylene glycol mono-R₁ -etherinclude:

ethylene glycol monomethyl ether (2-methoxyethanol; methyl Cellosolve);and ethylene glycol monoethyl ether (2-ethoxyethanol; Cellosolve); and

diethylene glycol monoethyl ether (2-[2-ethoxyethoxy]ethanol; Carbitol).

Illustrative alkanols having 1-4 carbon atoms include:

methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol),1-butanol, 2-butanol, and 2-methyl-1-propanol.

Illustrative mono-R₂ -ethers of "F" include:

ethylene glycol monobutyl ether

ethylene glycol monopentyl ether

ethylene glycol monohexyl ether

diethtylene glycol monobutyl ether

diethylene glycol monohexyl ether

Illustrative di-R-ethers of "G" include:

ethylene glycol dimethyl ether

ethylene glycol diethyl ether

ethylene glycol dibutyl ether

diethtylene glycol dimethyl ether

diethylene glycol diethyl ether

diethylene glycol dibutyl ether

triethylene glycol dimethyl ether

tetraethylene glycol dimethyl ether.

In using the dioxane solvent of "H", it is preferred to develop firstwith dioxane alone, followed by a mixture of dioxane and alkanol andfinished with alkanol alone (for example, dioxane/dioxane:methanolmixture/methanol).

Illustrative rinse nonsolvents of "I" include:

n-pentane, isopentane, n-hexane, n-heptane, n-octane, isooctane,methylcyclopentane, cyclohexane, dimethylcyclohexane, petroleum etherand ligroin.

Developer solvent/rinse nonsolvent combinations of particular interestinclude:

Schedule 1(III) and Schedule 3(E):

(1) ethylene glycol monoethyl ether acetate/ethylene glycol monoethylether;

(2) ethylene glycol monoethyl ether acetate/2-propanol.

These combinations are particularly effective with negative resistpolymers poly(4-chlorostyrene), poly(4-bromostyrene), andpoly(chloromethylstyrene).

It is to be understood that a developer solvent may be modified in itssolvent activity by the addition thereto of either a less effectivedeveloper solvent, or a rinse nonsolvent in the amount needed to obtaina solution mixture of the desired developer activity.

Illustrative of such solvent mixtures are:

ethylene glycol monobutyl ether diluted with n-octanol or with mixedwith octyl alcohol; and ethylene glycol monoethyl ether acetate dilutedwith ethylene glycol monoethyl ether.

Process II Development and Rinsing: General

It has been observed that after development with a developersolvent/rinse nonsolvent sequence, the thickness of the cross-linkedresist portions may still be somewhat greater than the originalthickness (height, elevation) of the initial unexposed resist layer.This is true not only for lines but also for large pads (areas), such as25 micrometer squares. The residual swelling was observed for thoseradiation doses just above the minimum required to obtain an image witha thickness equal to that of the initial unexposed resist layer. Thereis no residual swelling when the image is developed with a good solventand then is not rinsed with a nonsolvent, but this procedure causes moreor less severe snaking. Both snaking and residual swelling can besubstantially or totally eliminated by choosing a sequence of solventsand nonsolvents. The image is developed with a good solvent for theunexposed resist polymer. For some resists, an intermediate solvent maybe applied after the good solvent treatment. The developed resist isthen treated with a series of what would be poor solvents for theunexposed resist polymer. The developed resist is not allowed to dryduring the series of process rinses, which begins with a poor solventwhich has the greatest affinity for the exposed resist polymer and endswith a nonsolvent which has the least affinity for the exposed resistpolymer. It is thought this multiple rinsing procedure permits thegreatest amount of extraction of developer solvent and permits the mostnearly complete restoration of the negative resist image to its initialform (prior to development).

The process II procedure is illustrated by the development of exposedresist polymer poly(4-bromostyrene). The development treatment beginswith ethylene glycol monobutyl ether acetate, followed by ethyleneglycol monoethyl ether acetate. Next, the wet developed resist is rinsedwith nonsolvent ethylene glycol monoethyl ether, followed by 2-propanol.The final resist image, essentially free of snaking, is essentially thesame thickness as the initial resist polymer layer.

In both Processes I and II, the quality of the properly developed imagevaries with the radiation dose. With the optimum dose, a good cleanimage with the desired profile is obtained. As the dose is increasedbeyond the optimum, the lines get wider and the base areas of theprofile demonstrate an undesired widening.

Developer Solvent//Rinse Nonsolvents Combinations

Developer solvent//rinse nonsolvents combinations that are useful indevelopment of exposed resist and in straightening of snaky lines andedges and in decreasing swelling of the resist to about the initialresist thickness are presented in formula form in Schedule 2,hereinafter, where (a) and (b) show the sequential order of rinsing.

    ______________________________________                                        Schedule 2                                                                    ______________________________________                                        A.    (d/s)    R.sub.2 --OCH.sub.2 CH.sub.2).sub.m --O--H                           (r/ns)   (a) R.sub.5 --(OCH.sub.2 --CH.sub.2).sub.m --OH                               (b) R--OH                                                      B.    (d/s)    R.sub.7 --(OCH.sub.2 CH.sub.2).sub.m --O--R.sub.7                    (r/ns)   (a) R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH                                 (b) R--OH                                                      C.    (d/s)    R--CO--(OCH.sub.2 CH.sub.2).sub.p --O--(OC).sub.0-1 --R              (r/ns)   (a) R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH                                 (b) R--OH                                                      D.    (d/s)    R.sub.2 --(OCH.sub.2 CH.sub.2).sub.m --OH, mixed with                         R.sub.2 OH                                                           (r/ns)   (a) R.sub.2 --OH                                                              (b) R--OH                                                      ______________________________________                                    

where:

R is alkyl having 1-4 carbon atoms,

R₂ is alkyl having 4-8 carbon atoms,

R₅ is H, methyl or ethyl,

R₇ is alkyl having 1-8 carbon atoms,

m is an integer equal to 1-4, and

p is an integer equal to 1-2.

The specific developer solvent//rinse nonsolvents combinations useful indeveloping exposed resist and in straightening snaky lines and edges andedges and in decreasing swelling of the exposed resist to about theinitial resist thickness are presented in modified name form in Schedule4 below, where (a) and (b) show the sequential order of rinsing.

    ______________________________________                                        Schedule 4                                                                    ______________________________________                                        K.    (d/s)    ethylene glycol mono-R--ether acetate, or                                     diethylene glycol mono-R--ether acetate, or                                   mixtures thereof                                                     (r/ns)   (a) ethylene glycol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            L.    (d/s)    ethylene glycol mono-R.sub.2 --ether, or                                      diethylene glycol mono-R.sub.2 --ether, or                                    mixtures thereof                                                     (r/ns)   (a) ethylene gylcol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            M.    (d/s)    ethylene glycol di-R--ether, or                                               diethylene glycol di-R--ether, or                                             triethylene glycol di-R--ether, or                                            tetraethylene glycol di-R--ether, or                                          mixtures thereof                                                     (r/ns)   (a) ethylene glycol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            N.    (d/s)    ethylene glycol diacetate, or                                                 diethylene glycol diacetate, or                                               mixtures thereof                                                     (r/ns)   (a) ethylene glycol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            ______________________________________                                    

where:

R is alkyl having 1-4 carbon atoms,

R₁ is alkyl having 1-2 carbon atoms, and

R₂ is alkyl having 4-8 carbon atoms.

As in the aforesaid developer solvent/rinse nonsolvent treatmentprocedure, the wet resist condition is maintained between the varioustreatment steps of this developer solvent//rinse nonsolvents treatmentprocedure.

A variant procedure is carried out as follows: the first development iscarried out with the more effective solvent of the class set out in theparticular combination; then development proceeds further with a lesseffective solvent from that same class; then the rinse operation iscarried out as set out in that particular combination.

For example, the first development solvent treatment is with ethyleneglycol monobutyl ether acetate, and the second development solventtreatment is with ethylene glycol monoethyl ether acetate. This isfollowed by rinse nonsolvent ethylene glycol monoethyl ether, which inturn is followed by 2-propanol rinsing.

In another variant procedure, the developer solvent for a particularcombination is applied full strength. This is followed by a dilutedsolvent made up of a mixture of the first developer solvent and a rinsenonsolvent from that particular combination. Finally, the rinsenonsolvent sequence treatment is applied.

For example, the exposed resist is first treated with developer solventfrom combination "K", ethylene glycol monoethyl ether acetate. This isfollowed with 1:2, by volume, of a mixture of ethylene glycol monoethylether acetate:ethylene glycol monoethyl ether. This is in turn followedwith the rinse nonsolvent sequence, ethylene glycol monoethyl ether andthen 2-propanol.

Still another variant involves using two or more rinse nonsolvents fromthe same class, sequentially, in the rinse procedure. For example,rinsing with 2-propanol is followed by rinsing with methanol.

Developer solvent//rinse nonsolvents combinations of particularinterest, in addition to the variants above, include:

Schedule 4(K):

ethylene glycol monoethyl ether acetate//ethylene glycol monoethylether/2-propanol.

This combination is particularly effective with negative resist polymerspoly(4-chlorostyrene), poly(3-chlorostyrene), poly(chloromethylstyrene),poly(2,6-dichlorostyrene), and poly(2,5-dichlorostyrene).

Schedule 4(M):

ethylene glycol monobutyl ether//ethylene glycol monoethylether/2-propanol.

This combination is particularly effective with the negative resistpolymer poly(4-bromostyrene).

Schedule 2(D):

A 1:2 mixture of 2-butoxyethanol and 1-octanol//1-octanol/2-propanol.

This combination is particularly effective with negative resist polymerpoly(4-tertbutylstyrene).

Process III Bonding of Resist Polymer to Siliceous Substrate Utilizing aSilane Interlayer

Less than satisfactory adhesion existed between the hereinbefore definedstyrene resist polymers and the siliceous substrate after development,in some instances.

The problem was solved by use of a silane interlayer between the styreneresist polymer and the siliceous substrate. The silane interlayer wasapplied directly to the surface of the siliceous substrate and theinterlayer-coated surface was heated to a temperature sufficient forbonding; afterward, a layer of the styrene resist polymer was applied,overlaying the silane layer. The styrene resist polymer surface was thenirradiated to simultaneously form the desired pattern image and bondthis patterned image area to the silane layer. The bondedpolymer-silane-substrate is a substantially unitary article.

It is indicated that the silane/irradiation bonding technique isapplicable to any polymeric material which responds to radiation byproducing free radicals. Such polymeric materials include, but are notlimited to: polystyrene, halogenated polystyrene, and substitutedstyrene polymers having at least one substituent, where thesubstituent(s) is independently selected from the group consisting ofalkyl having 1-4 carbon atoms, halo, haloalkyl having 1-4 carbon atomsand at least one halo, and mixtures thereof.

The substrates for this bonding process include any materials which havesilica or silicon present at the surface of the substrate in amountssufficient to provide the desired degree of bonding. Such substratesinclude, but are not limited to, silicon, silicon dioxide, fused quartz,fused silica and silica-containing glass.

Definition of Silane

When the International union of Pure and Applied Chemistry (IUPAC)issued the rules on naming of acid halides and like compounds, thealkane and alkene series were parted at the six carbon atom compounds.The suffix, "oyl", is applied to the alkane or alkene name afterdropping the final "e". However, in deference to the long time usage inboth science and commerce of common names for the 1-5 carbon atomcontent compounds, the common names are accepted along with the IUPACnaming. Thus, we have formyl, acetyl, propionyl, butyryl, valeryl,acryl, methacryl, etc.

However, when one wishes to set forth formula series of compounds, the"yl" common names impede clarity. For this reason, the "oyl" naming isused herein, except when giving illustrations which follow the commonname conventions.

The silanes which are useful in this bonding process of this inventionare:

    R.sup.i --(O).sub.0-1 --(R.sup.ii).sub.0-1 --Si--(R.sup.iii).sub.3

where:

R^(i) is acryloyl, methacryloyl, or vinyl; when R^(i) is vinyl, then themoiety "(O)₀₋₁ " is absent;

R^(ii) is alkylene having 2-6 carbon atoms, or R^(iv) --NH--R^(v), whereR^(iv) is hydroxyalkylene having 2-6 carbon atoms and R^(v) is alkylenehaving 2-6 carbon atoms, and when R^(i) is vinyl, R^(ii) is absent;

R^(iii) is halo, or alkoxy having 1-6 carbon atoms, or alkoxyalkoxyhaving at least 3-6 carbon atoms, or alkanoyloxy having a total of 2-5carbon atoms, or an alkyl having 1-6 carbon atoms, where the number ofsaid alkyl groups present is not more than 2, or mixtures of thepreceding.

The layer applied to the surface of the siliceous substrate may also bethe hydrolysis product of any of the above described silanes, whereinone or more of the R^(iii) groups are replaced by OH.

Bonding Process

In the process of the invention, a substantially unitary article isformed, comprising a siliceous substrate (as defined above), a layer ofsilane (as defined above) applied to a surface of the substrate, and apolymer resin (as defined above) overlaying the silane.

The silane is bonded to the siliceous substrate by heating thesilane-coated surface to about 200° C. for a period of about fiveminutes. The polymer resin is then applied over the silane coatedsurface, and the polymer-coated surface is irradiated to generate freeradicals therein, to form the bond between the polymer and the silane.The final, resultant article is substantially unitary.

A preferred silane in the practice of the invention is3-methacryloxypropyltrimethyoxysilane (common name); herein referred toas MTS or ##STR1##

The following listing of silane compounds suitable for use in thebonding process of this invention is taken from a textbook which usedthe common name style:

methacryloxypropyldimethylchlorosilane

3-methacryloxypropyldimethylethoxysilane

methacryloxypropylmethyldichlorosilane

3-methacryloxypropylmethyldiethoxysilane

3-methacryloxypropyltrichlorosilane

3-methacryloxypropyltrimethoxysilane

3-methacryloxypropyltris(methoxyethoxy)silane

N-(3-acryloxy-2-hydroxypropyl)-3-amino-propyltriethoxysilane

vinyldimethylchlorosilane

vinyldimethylethoxysilane

vinylethyldichlorosilane

vinylmethyldiacetoxysilane

vinylmethyldichlorosilane

vinylmethyldiethoxysilane

vinyltriacetoxysilane

vinyltrichlorosilane

vinyltriethoxysilane

vinyltriisopropoxysilane

vinyltrimethoxysilane

vinyltris(2-methoxyethoxy)silane

EXAMPLE OF SILANE BONDING

The substrate comprised a silicon wafer. A thin film of a preferredsilane (MTS) was applied to one surface of the wafer from toluenesolution. Solutions containing from 0.04-4 volume percent silane havebeen used. The coated wafer was heated to about 200° C. for five minutesin an oven. The dry wafer was coated by spin coating withpoly(4-chlorostyrene). The article was irradiated to form a resistpattern image therein. The latent image was developed according to theprocedure of Process II hereinbefore. The developed resist image wasfirmly bonded to the substrate; it appeared that the sandwich had becomea substantially unitary structure or article.

Without subscribing to any particular theory, it is thought that whenthe resist polymer is irradiated, the free radicals generated react withthe olefinic double bond in the MTS, thereby anchoring the crosslinkedresist image to the MTS silane layer. It is possible, but not knownwhether such irradiation also activates groups(s) in the MTS to reactwith groups on the silicon substrate surface.

EXAMPLES OF PROCESS I AND II

In the process I examples 1-7 and in process II examples 8 and 10-13,the operation was carried out as follows:

The negative resist material was poly(4-chlorostyrene) of weight averagemolecular weight of 2.9×10⁵ and dispersivity of 3.0. Resist solutionswere prepared in chlorobenzene solvent, spin-coated on silicon wafersand baked at 50°-90° C. in a vacuum. Coated wafers were exposed with 20keV electrons with a vector scan electron beam system. The patterns usedincluded a matrix of 25 micrometer squares for evaluating sensitivityand a pattern consisting of twenty sets of five single-pass linescovering each decade of dose to evaluate line shape and profiles. Waferswere dip developed and rinsed in a series of developer solvents andrinse nonsolvents, or spray developed with a Thayer and Chandler air gunheld about six inches from the wafer and then dip rinsed in a differentdeveloper solvent, followed by rinse nonsolvent. All images were blowndry in nitrogen and then baked at 60° C. in a vacuum for thirty minutesto remove rinse nonsolvent.

This sequential procedure resolved lines that were 0.3 micrometers wide,0.6 micrometers high, placed on 0.7 micrometer line centers. These lineshad excellent resistance to etching with a CF₄ +O₂ plasma. It waspossible by the multiple rinse procedure of the invention to produceimages without snaking and of a thickness essentially that of theinitial resist coating, with lines that were as narrow as 0.25micrometer in 0.5 micrometer thick resist coating, these lines havingexcellent profiles and straight sidewalls.

Also, it was observed that when the image was developed by usingdeveloper solvent alone, the lines in the image snaked very badly. Inprocess II, examples 9 and 15-19, the operation differed from theoperation described previously only as specified in the example.

EXAMPLES OF PROCESS I EXAMPLE 1

The first developer solvent was dioxane alone, dipped for 15 seconds.The following developer solvent was a solution mixture, 2:1, of dioxaneand methanol, dipped for 15 seconds. The developed resist, still wet,was dipped into methanol for 300 seconds. The finished resist lines hadan excellent appearance in terms of snaking and profile.

EXAMPLE 2

The developer solvent was ethylene glycol monoethyl ether acetate(2-ethoxyethyl acetate) applied in two sequential portions, dipping for15 seconds in each portion; 2-propanol was the rinse nonsolvent, dippingfor 180 seconds. The appearance of the image lines was excellent.

EXAMPLE 3

The developer solvent was ethylene glycol monoethyl ether acetateapplied in two sequential portions, dipping for 15 seconds in eachportion. Methanol was the rinse nonsolvent, dipping for 180 seconds. Theappearance of the finished image lines was good when examined by anoptical microscope.

EXAMPLE 4

The developer solvent was ethylene glycol monoethyl ether acetate,applied in two sequential portions, dipping for 20 seconds and 10seconds, respectively. The rinse nonsolvent was ethylene glycolmonoethyl ether (2-ethoxyethanol), dipping for 180 seconds. The lineappearance optically was good.

EXAMPLE 5

The development/rinse operation was as in Example 4, except that therinse nonsolvent was methanol. The optical appearance of the lines wasgood, but with some minor dimensional distortions.

EXAMPLE 6

The development/rinse operation was as in Example 4, except that therinse nonsolvent was 2-propanol. The optical appearance of the finishedlines was good, but with some minor dimensional distortions.

EXAMPLE 7

The developer solvent was monochlorobenzene, applied in two sequentialportions, dipping for 15 seconds in each portion. The rinse nonsolventwas heptane, dipped for 180 seconds. The finished lines looked goodoptically.

EXAMPLES OF PROCESS II EXAMPLE 8

The developer solvent was ethylene glycol monoethyl ether acetate,applied in two 15 second sequential dips. The first rinse nonsolvent was2-propanol, applied immediately, dipped for 180 seconds. The secondrinse nonsolvent, applied immediately, was methanol, dipped for 180seconds. The finished lines looked good optically.

EXAMPLE 9

An image was written in a coating of poly(2,6-dichlorostyrene) on asilicon wafer using a 20 keV electron beam. The image was developedusing 2-ethoxyethyl acetate, applied in two 30 second sequential dips.The first rinse nonsolvent, applied immediately, was 2-ethoxyethanol,dipped for 60 seconds. The second rinse nonsolvent, applied immediately,was 2-propanol dipped for 60 seconds. The finished lines were good withrespect to snaking and resist height.

EXAMPLE 10

Ethylene glycol monoethyl ether acetate was the developer solvent,applied in two 15 second dips. The first rinse nonsolvent, appliedimmediately, was ethylene glycol monoethyl ether, dipped for 60 seconds.The second rinse nonsolvent, applied immediately, was 2-propanol, dippedfor 60 seconds. The last rinse nonsolvent was methanol, dipped for 180seconds. The finished lines were excellent with respect to snaking andto resist height.

EXAMPLE 11

Ethylene glycol monoethyl ether acetate was the developer solvent,applied in two 30 second dips. The first rinse nonsolvent was ethyleneglycol monoethyl ether, dipped for 60 seconds. The second rinsenonsolvent was 2-propanol, dipped for 60 seconds. The last rinsenonsolvent was methanol, dipped for 60 seconds. The finished lines werevery good with respect to snaking and to resist height.

EXAMPLE 12

The developer solvent was ethylene glycol monoethyl ether acetate,applied in two 30 second dips. The first rinse nonsolvent was ethyleneglycol monoethyl ether, dipped for 60 seconds. The second rinsenonsolvent was 2-propanol, dipped for 60 seconds. The finished lineswere excellent with respect to snaking and to resist height. The lineardose was 2.82×10⁻¹⁰ C/cm. Line width was 0.21 micrometer and height was1.1 micrometer.

EXAMPLE 13

The first developer solvent was ethylene glycol monoethyl ether acetate,dipped for 15 seconds. The second developer solvent was a 1:2 solutionmixture of ethylene glycol monoethyl ether acetate and ethylene glycolmonoethyl ether (a rinse nonsolvent), dipped for 15 seconds. The firstrinse nonsolvent was ethylene glycol monoethyl ether, dipped for 60seconds. The second rinse nonsolvent was 2-propanol, dipped for 60seconds. The finished lines were excellent with respect to snaking andresist height. The linear dose was 3.9×10⁻¹⁰ C/cm. The linewidth was 0.4micrometer and gapwidth was 0.75 micrometer.

EXAMPLE 14

The developer solvent was diethylene glycol monobutyl ether, applied intwo portions, dipped for 60 seconds and 30 seconds, respectively. Thefirst rinse nonsolvent, applied immediately, was ethylene glycolmonoethyl ether, dipped for 45 seconds. The second rinse nonsolvent,applied immediately, was 2-propanol, dipped for 60 seconds. The finishedlines were good optically with respect to snaking and resist height.

EXAMPLE 15

The resist polymer was poly(4-bromostyrene); this was dosed withradiation at 10⁻⁴ to 10⁻⁵ C/cm². The first developer solvent wasethylene glycol monobutyl ether acetate, dipped for 60 seconds. Thesecond developer solvent was ethylene glycol monoethyl ether acetate,dipped for 30 seconds. The first rinse nonsolvent, applied immediately,was ethylene glycol monoethyl ether, dipped for 60 seconds. The secondrinse nonsolvent, applied immediately, was 2-propanol, dipped for 15seconds. The finished lines were excellent with respect to snaking andresist height.

EXAMPLE 16

An image was written in a 500 angstrom thick coating ofpoly(4-tert-butylstyrene) on a silicon wafer using a 70 keV Ga⁺ beam.The image was developed using a 3:1 mixture of octylalcohol:2-butoxyethanol, applied in two sequential dips of 60 secondseach. The first rinse nonsolvent, applied immediately, was octylalcohol, dipped for 60 seconds. The second rinse nonsolvent, appliedimmediately, was isopropyl alcohol, dipped for 60 seconds. The finishedlines were narrow and straight.

EXAMPLE 17

An image was written in a 1,500 angstrom thick coating ofpoly(2,5-dichlorostyrene) on a silicon wafer using a 70 keV Si⁺⁺ beam.The image was developed using 2-ethoxyethyl acetate, applied in twosequential dips of 30 seconds each. The first rinse nonsolvent, appliedimmediately, was 2-ethoxyethanol, dipped for 60 seconds. The secondrinse nonsolvent, applied immediately, was isopropyl alcohol, dipped for60 seconds. The finished lines were moderately good optically, withrespect to line width and were good with respect to snaking and resistheight.

EXAMPLE 18

An image was written in 6,000 angstrom thick coating ofpoly(3-chlorostyrene) on a silicon wafer using a 20 keV electron beam.One image was developed using each of the following two procedures:

(1) The image was developed using 2-ethoxyethyl acetate, applied in twosequential dips of 15 seconds each. The first rinse nonsolvent, appliedimmediately, was 2-ethoxyethanol, dipped for 60 seconds. The secondrinse nonsolvent, applied immediately, was isopropyl alcohol, dipped for180 seconds.

(2) The image was developed using 2-butoxyethyl acetate, applied in twosequential dips of 20 seconds followed by 10 seconds. The first rinsenonsolvent, applied immediately, was 2-ethoxyethanol, dipped for 60seconds. The second rinse nonsolvent, applied immediately, was isopropylalcohol, dipped for 180 seconds.

The finished lines were very straight and the line profiles wereexcellent for both of the procedures described in this example.

It is obvious that the development and rinsing procedures described inProcess I and Process II can be used independently of the bondingprocedure described in Process III and still result in substantialimprovement in the production of negative resists over those obtainableusing the prior art. However, it is the use of the bonding procedure inpreparation of the exposed negative resist image combined with thedevelopment and rinse procedure described in Process I or Process IIwhich permits maximum benefit from the teachings of this invention.

What is claimed is:
 1. A lithographic process for preparing a patternedresist on a substrate, which process comprises:(1) applying a layer ofnegative resist polymer onto a substrate, said polymer being selectedfrom the group consisting of:(a) polystyrene (b) halogenatedpolystyrene, and (c) substituted styrene polymer having at least onesubstituent, where said at least one substituent is independentlyselected from the group consisting of alkyl having 1-4 carbon atoms;halo; haloalkyl having 1-4 carbon atoms and at least one halo, and (d)mixtures thereof; (2) irradiating said resist polymer layer to form anegative pattern image therein; and (3) developing said image by(i)dissolving away unexposed polymer with a developer solvent, and (ii)rinsing said wet developed resist with a nonsolvent to eliminatesubstantially any snakiness of the developed resist pattern image;wheresaid developer solvent/rinse nonsolvent combination is selected from thefollowing schedule, wherein (d/s) is the developer solvent and (r/ns) isrinse nonsolvent:

    ______________________________________                                        Schedule 1                                                                    ______________________________________                                        I.   (d/s)    R.sub.2 --(OCH.sub.2 CH.sub.2).sub.m --O--H                          (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              II.  (d/s)    R.sub.7 --(OCH.sub.2 CH.sub.2).sub.m --O--R.sub.7                    (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              III. (d/s)    R--CO--(OCH.sub.2 CH.sub.2).sub.p --O--(OC).sub.0-1 --R              (r/ns)   R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH or R--OH              IV.  (d/s)    benzene, toluene, ethylbenzene, xylene,                                       monochlorobenzene, monochlorotoluene,                                         monochloroethylbenzene, monochloroxylene,                                     ortho-dichlorobenzene, meta-dichloro-                                         benzene, and trichlorobenzene                                        (r/ns)   alkane having 5-8 carbon atoms, cyclo-                                        alkane having 5-8 carbon atoms, and                                           petroleum distillate boiling in the 5-8                                       alkane carbon atom boiling range                                V.   (d/s)    dioxane                                                              (r/ns)   R--OH                                                           ______________________________________                                    

where: R is alkyl having 1-4 carbon atoms, R₂ is alkyl having 4-8 carbonatoms, R₅ is H, methyl, or ethyl, R₇ is alkyl having 1-8 carbon atoms, mis an integer equal to 1-4, and p is an integer equal to 1-2.
 2. Theprocess of claim 1 wherein said resist polymer is poly(3-chlorostyrene).3. The process of claim 1 wherein said resist polymer ispoly(4-chlorostyrene).
 4. The process of claim 1 wherein said resistpolymer is poly(2,5-dichlorostyrene).
 5. The process of claim 1 whereinsaid resist polymer is poly(2,6-dichlorostyrene).
 6. The process inclaim 1 wherein said resist polymer is poly(3,4-dichlorostyrene).
 7. Theprocess in claim 1 wherein said resist polymer is poly(4-bromostyrene).8. The process of claim 1 wherein said resist polymer ispoly(chloromethylstyrene).
 9. The process in claim 1 wherein said resistpolymer is poly(4-tert-butylstyrene).
 10. The process of claim 1 whereinsaid resist polymer is poly(4-chlorostyrene) and said developer/rinsecombination III is ethylene glycol monoethyl ether acetate/2-propanol.11. The process of claim 1 wherein said resist polymer ispoly(4-chlorostyrene) and said developer/rinse combination is ethyleneglycol monoethyl ether acetate/ethylene glycol monoethyl ether.
 12. Alithographic process for preparing a patterned resist on a substrate,which process comprises:(1) applying a layer of negative resist polymeronto a substrate, said polymer being selected from the group consistingof:(a) polystyrene, (b) halogenated polystyrene, and (c) substitutedstyrene polymer having at least one substituent, said at least onesubstituent is selected from the group consisting of alkyl having 1-4carbon atoms; halo; haloalkyl having 1-4 carbon atoms and at least onehalo, and (d) mixtures thereof; (2) irradiating said resist polymer toform a negative pattern image therein; and (3) developing said imageby(i) dissolving away unexposed polymer with a developer solvent, and(ii) rinsing said wet developed resist with a nonsolvent to eliminatesubstantially any snakiness of the developed resist pattern image; wheresaid developer solvent/rinse nonsolvent combination is selected from thefollowing schedule, wherein (d/s) is developer solvent and (r/ns) isrinse nonsolvent:

    ______________________________________                                        E.   (d/s)    ethylene glycol mono-R--ether acetate, or                                     diethylene glycol mono-R--ether acetate,                                      or mixtures thereof                                                  (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 F.   (d/s)    ethylene glycol mono-R.sub.2 --ether, or                                      diethylene glycol mono-R.sub.2 --ether, or                                    mixtures thereof                                                     (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 G.   (d/s)    ethylene glycol di-R--ether, or                                               diethylene glycol di-R--ether, or                                             triethylene glycol di-R--ether, or                                            tetraethylene glycol di-R--ether, or                                          mixtures thereof                                                     (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 H.   (d/s)    ethylene glycol diacetate, or                                                 diethylene glycol diacetate, or                                               triethylene glycol diacetate, or                                              mixtures thereof                                                     (r/ns)   ethylene glycol mono-R.sub.1 --ether, or                                      alkanol having 1-4 carbon atoms                                 I.   (d/s)    dioxane                                                              (r/ns)   alkanol having 1-4 carbon atoms                                 J.   (d/s)    benzene, toluene, ethylbenzene, xylene,                                       monochlorobenzene, monochlorotoluene,                                         monochloroethylbenzene, monochloro-                                           xylene, ortho-dichlorobenzene, meta-                                          dichlorobenzene, and trichlorobenzene                                (r/ns)   alkane having 5-8 carbon atoms, cycloalkane                                   having 5-8 carbon atoms, and petroleum                                        distillate boiling in the 5-8 alkane                                          carbon atom boiling range                                       ______________________________________                                    

where: R is alkyl having 1-4 carbon atoms, R₁ is alkyl having 1-2 carbonatoms, and R₂ is alkyl having 4-8 carbon atoms.
 13. The process of claim12 wherein said developer/rinse combination of "E" is ethylene glycolmonoethyl ether acetate/ethylene glycol monoethyl ether.
 14. The processof claim 12 wherein said developer/rinse combination of "E" is ethyleneglycol monoethyl ether acetate/2-propanol.
 15. The process of claim 12wherein said developer/rinse combination of "F" is ethylene glycolmonobutyl ether/ethylene glycol monoethyl ether.
 16. The process ofclaim 12 wherein said developer/rinse combination of "I" isdioxane/dioxane:methanol mixture/methanol.
 17. A lithographic processfor preparing a patterned resist on a substrate, which processcomprises:(1) applying a layer of negative resist polymer onto asubstrate, said polymer being selected from the group consisting of:(a)polystyrene, (b) halogenated polystyrene, and (c) substituted styrenepolymer having at least one substituent, where said at least onesubstituent is selected from the group consisting of alkyl having 1-4carbon atoms; halo; haloalkyl having 1-4 carbon atoms and at least onehalo, and (d) mixtures thereof; (2) irradiating said resist polymer toform a negative pattern image therein; and (3) developing said imageby:(i) dissolving away unexposed polymer with a developer solvent, and(ii) multiply rinsing said wet developed resist using a series ofconsecutive rinses employing successively weaker solvents, andmaintaining the resist in a wetted condition throughout the consecutiverinses, so as to substantially eliminate any snakiness of the developedresist pattern image and to shrink any swelling of the developed resistprofile, so that the developed resist image is substantially the sameshape and height as the initial exposed image prior to development,wherethe combination of developer solvent and rinse are selected from thefollowing schedule, wherein (d/s) is developer solvent and (r/s)represents the rinse solvents wherein the rinse series begins withrinses selected from (a) or a mixture of (a) and (b) which is rich in(a) and progresses toward rinses richer in (b) or with only (b), andwhere the series of rinses encompasses a minimum of two rinses:

    ______________________________________                                        A.     (d/s)   R.sub.2 --(OCH.sub.2 CH.sub.2).sub.m --O--H                           (r/s)   (a) R.sub.5 --(OCH.sub.2 --CH.sub.2).sub.m --OH                               (b) R--OH                                                      B.     (d/s)   R.sub.7 --(OCH.sub.2 CH.sub.2).sub.m --O--R.sub.7                     (r/s)   (a) R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH                                 (b) R--OH                                                      C.     (d/s)   R--CO--(OCH.sub.2 CH.sub.2).sub.p --O--(OC).sub.0-1 --R               (r/s)   (a) R.sub.5 --(OCH.sub.2 CH.sub.2).sub.m --OH                                 (b) R--OH                                                      D.     (d/s)   R.sub.2 --(OCH.sub.2 CH.sub.2).sub.m --OH, mixed with                         R.sub.2 OH                                                            (r/s)   (a) R.sub.2 --OH                                                              (b) R--OH                                                      ______________________________________                                    

where: R is alkyl having 1-4 carbon atoms, R₂ is alkyl having 4-8 carbonatoms, R₅ is H, methyl or ethyl, R₇ is alkyl having 1-8 carbon atoms, mis an integer equal to 1-4, and p is an integer equal to 1-2.
 18. Theprocess of claim 17 wherein said negative resist polymer is selectedfrom the group consisting of poly(3-chlorostyrene),poly(4-chlorostyrene), poly(2,5-dichlorostyrene),poly(2,6-dichlorostyrene), poly(3,4-dichlorostyrene),poly(4-bromostyrene), poly(chloromethylsyrene) andpoly(4-tert-butylstyrene).
 19. The process of claim 18 wherein saiddeveloper and rinse combination of "C" is ethylene glycol monoethylether acetate developer solvent and ethylene glycol monoethyl ether as(a) 2-propanol as (b).
 20. The process of claim 18 wherein saiddeveloper and rinse combination of "B" is ethylene glycol monobutylether as developer solvent and ethylene glycol monoethyl ether as (a)2-propanol as (b).
 21. A lithographic process for preparing a patternedresist on a substrate, which process comprises:(1) applying a layer ofnegative resist polymer onto a substrate, said polymer being selectedfrom the group consisting of:(a) polystyrene, (b) halogenatedpolystyrene, and (c) substituted styrene polymer having at least onesubstituent, where said at least one substituent is selected from thegroup consisting of alkyl having 1-4 carbon atoms; halo; haloalkylhaving 1-4 carbon atoms and at least one halo, and (d) mixtures thereof;(2) irradiating said resist polymer to form a negative pattern imagetherein; and (3) developing said image by:(i) dissolving away unexposedpolymer with a developer solvent, and (ii) multiply rinsing said wetdeveloped resist using a series of consecutive rinses employingsuccessively weaker solvents, and maintaining the resist in a wettedcondition throughout the consecutive rinses, so as to substantiallyeliminate any snakiness of the developed resist pattern image and toshrink any swelling of the developed resist profile, so that thedeveloped resist image is substantially the same as the initial exposedimage prior to development,where the combination of developer solventand rinse are selected from the following schedule, wherein (d/s) isdeveloper solvent and (r/s) represents the rinse solvents wherein therinse series begins with rinses selected from (a) or a mixture of (a)and (b) which is rich in (a) and progresses toward rinses richer in (b)or with only (b), and where the series of rinses encompasses a minimumof two rinses:

    ______________________________________                                        K.     (d/s)   ethylene glycol mono-R--ether acetate, or                                     diethylene glycol mono-R--ether acetate, or                                   mixture thereof                                                       (r/s)   (a) ethylene glycol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            L.     (d/s)   ethylene glycol mono-R.sub.2 --ether, or                                      diethylene glycol mono-R.sub.2 --ether, or                                    mixtures thereof                                                      (r/s)   (a) ethylene glycol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            M.     (d/s)   ethylene glycol di-R--ether, or                                               diethylene glycol di-R--ether, or                                             triethylene glycol di-R--ether, or                                            tetraethylene glycol di-R--ether, or                                          mixtures thereof                                                      (r/s)   (a) ethylene glycol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            N.     (d/s)   ethylene glycol diacetate, or                                                 diethylene glycol diacetate, or                                               mixtures thereof                                                      (r/s)   (a) ethylene glycol mono-R.sub.1 --ether                                      (b) alkanol having 1-4 carbon atoms                            ______________________________________                                    

where: R is alkyl having 1-4 carbon atoms, R₁ is alkyl having 1-2 carbonatoms, and R₂ is alkyl having 4-8 carbon atoms.
 22. The process of claim21 wherein said negative resist polymer is selected from the groupconsisting of poly(3-chlorostyrene), poly(4-chlorostyrene),poly(2,5-dichlorostyrene), poly(2,6-dichlorostyrene),poly(3,4-dichlorostyrene), poly(4-bromostyrene),poly(chloromethylstyrene) and poly(4-tert-butylstyrene).
 23. The processof claim 22 wherein said developer and rinse combination of "K" isethylene glycol monoethyl ether acetate as developer solvent andethylene glycol monoethyl ether as (a) 2-propanol as (b).
 24. Theprocess of claim 21 wherein said developer and rinse combination of "K"is ethylene glycol monobutyl ether acetate and ethylene glycol monoethylether acetate as developer and ethylene glycol monoethyl ether as (a)2-propanol as (b).